1. Field of the Invention
This invention generally relates to a gas extracting device which is used to analyze gas suspended or dissolved in a liquid, such as an insulating oil, in order to check the abnormal state of an electric apparatus regarding electric power of a transformer, reactor etc., using the insulating oil.
2. Description of the Prior Art
In general, there are typically three types of gas extracting devices for extracting gas suspended in the insulating oil., ine., a Torricelli's vacuum type, a combination of a mercury diffusion pump and Toepler pump type, and a combination of a vacuum pump and a moving valve type of gas extracting device.
In the Torricelli's vacuum type gas extracting device, the so-called Torricelli's vacuum is first produced by using a level bottle made of glass filled with the mercury, and forcing a gas suspended in the insulating oil to be extracted into a vessel made of glass which is vacuum state. Due to usage of mercury and the vessel made of glass, this device is accordingly inconvenient in that scattering of mercury and damage to the glass vessel may occur as a result of an accident.
Moreover, in the mercury diffusion pump and Toepler pump type of gas extracting device, by using an oil rotary pump, a mercury diffusion pump and a Toepler pump, the interior of a desired vessel made of glass is first maintained in a vacuum state. Then, by injecting the insulating oil into the desired vessel, the gas suspended in the oil is extracted and stored in a gas accumulating vessel. There is, however, some danger of the mercury scattering and the vessel being damaged as could occur in the above-mentioned Toricelli's vacuum type device.
Furthermore, in the third type, i.e., the vacuum pump and moving valve type of gas extracting device, the interior of a vessel, i.e., a cylinder, is first maintained in a vacuum state by the vacuum pump. After completely extracting the gas into the cylinder, the gas is guided into a gas accumulating tube by operation of the moving valve. However, the moving valve, i.e., the piston coupled with the cylinder, can only be moved once by switching over the valves associated with and mounted on both sides of the cylinders because pressures at both ends of cylinder chamber become equal. Accordingly, it is difficult to fully extract the gas highly suspended in the oil and to measure the quantity of the suspended gas with accuracy.
Furthermore, besides the three types above mentioned, there is also known a carrier gas replacing type of gas extracting device in which the gas in the insulating oil is drawn out from the oil by directly injecting the carrier gas into the oil, or by bubbling the carrier gas. In the case where a low concentration of suspended gas being present it is, however, difficult to measure the quantity of suspended gas with accuracy because of the relatively small quantity of insulating oil to be analyzed which can be obtained at one time.